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Characterizing Arctic mixed-phase cloud structure and its relationship with humidity and temperature inversion using ARM NSA observations
In this work, the characteristics of the Arctic mixed-phase cloud (AMC) have been investigated using data collected at the Atmospheric Radiation Measurement North Slope Alaska site from October 2006 to September 2009. AMC has an annual occurrence frequency of 42.3%, which includes 18.7% of single-layered AMCs and 23.6% for multiple layers. Two cloud base heights (CBHs) are defined from ceilometer and micropulse lidar (MPL) measurements. For single-layered AMC, the ceilometer-derived CBH represents the base of the liquid-dominant layer near the cloud top, while MPL-derived CBH represents base of the lower ice-dominant layer. The annual mean CBHs from ceilometer and MPL measurements are 1.0 km and 0.6 km, respectively, with the largest difference (~1.0 km) occurring from December to March and the smallest difference in September. The humidity inversion occurrence decreases with increasing humidity inversion intensity (stronger in summer than in winter). During the winter months, AMC occurrences increase from 15% to 35% when the inversion intensity increases from 0.1 to 0.9 g/kg. On the contrary, despite a higher frequency of strong humidity inversion in summer, AMC occurrences are nearly invariant for different inversion intensities. On average, humidity and temperature inversion frequencies of occurrence above an AMC are 5 and 8 times, respectively, as high as those below an AMC. The strong inversion occurrences for both humidity and temperature above an AMC provide the moisture sources from above for the formation and maintenance of AMCs. In conclusion, this result helps to reconcile the persistency of AMCs even when the Arctic surface is covered by snow and ice.
Evaluation of high‐level clouds in cloud resolving model simulations with ARM and KWAJEX observations
Abstract In this study, we evaluate high‐level clouds in a cloud resolving model during two convective cases, ARM9707 and KWAJEX. The simulated joint histograms of cloud occurrence and radar reflectivity compare well with cloud radar and satellite observations when using a two‐moment microphysics scheme. However, simulations performed with a single moment microphysical scheme exhibit low biases of approximately 20 dB. During convective events, two‐moment microphysical overestimate the amount of high‐level cloud and one‐moment microphysics precipitate too readily and underestimate the amount and height of high‐level cloud. For ARM9707, persistent large positive biases in high‐level cloud are found, which are not sensitive to changes in ice particle fall velocity and ice nuclei number concentration in the two‐moment microphysics. These biases are caused by biases in large‐scale forcing and maintained by the periodic lateral boundary conditions. The combined effects include significant biases in high‐level cloud amount, radiation, and high sensitivity of cloud amount to nudging time scale in both convective cases. The high sensitivity of high‐level cloud amount to the thermodynamic nudging time scale suggests that thermodynamic nudging can be a powerful “tuning” parameter for the simulated cloud and radiation but should be applied with caution. The role of the periodic lateral boundary conditions in reinforcing the biases in cloud and radiation suggests that reducing the uncertainty in the large‐scale forcing in high levels is important for similar convective cases and has far reaching implications for simulating high‐level clouds in super‐parameterized global climate models such as the multiscale modeling framework.
CAUSES: Diagnosis of the Summertime Warm Bias in CMIP5 Climate Models at the ARM Southern Great Plains Site
Abstract All the weather and climate models participating in the Clouds Above the United States and Errors at the Surface project show a summertime surface air temperature (T2 m) warm bias in the region of the central United States. To understand the warm bias in long‐term climate simulations, we assess the Atmospheric Model Intercomparison Project simulations from the Coupled Model Intercomparison Project Phase 5, with long‐term observations mainly from the Atmospheric Radiation Measurement program Southern Great Plains site. Quantities related to the surface energy and water budget, and large‐scale circulation are analyzed to identify possible factors and plausible links involved in the warm bias. The systematic warm season bias is characterized by an overestimation of T2 m and underestimation of surface humidity, precipitation, and precipitable water. Accompanying the warm bias is an overestimation of absorbed solar radiation at the surface, which is due to a combination of insufficient cloud reflection and clear‐sky shortwave absorption by water vapor and an underestimation in surface albedo. The bias in cloud is shown to contribute most to the radiation bias. The surface layer soil moisture impacts T2 m through its control on evaporative fraction. The error in evaporative fraction is another important contributor to T2 m. Similar sources of error are found in hindcast from other Clouds Above the United States and Errors at the Surface studies. In Atmospheric Model Intercomparison Project simulations, biases in meridional wind velocity associated with the low‐level jet and the 500 hPa vertical velocity may also relate to T2 m bias through their control on the surface energy and water budget.
Assessment of Uncertainty in Cloud Radiative Effects and Heating Rates through Retrieval Algorithm Differences: Analysis using 3-years of ARM data at Darwin, Australia
Ground-based radar and lidar observations obtained at the Department of Energy’s Atmospheric Radiation Measurement Program’s Tropical Western Pacific site located in Darwin, Australia are used to retrieve ice cloud properties in anvil and cirrus clouds. Cloud microphysical properties derived from four different retrieval algorithms (two radar-lidar and two radar only algorithms) are compared by examining mean profiles and probability density functions of effective radius (Re), ice water content (IWC), extinction, ice number concentration, ice crystal fall speed, and vertical air velocity. Retrieval algorithm uncertainty is quantified using radiative flux closure exercises. The effect of uncertainty in retrieved quantities on the cloud radiative effect and radiative heating rates are presented. Our analysis shows that IWC compares well among algorithms, but Re shows significant discrepancies, which is attributed primarily to assumptions of particle shape. Uncertainty in Re and IWC translates into sometimes-large differences in cloud radiative effect (CRE) though the majority of cases have a CRE difference of roughly 10 W m-2 on average. These differences, which we believe are primarily driven by the uncertainty in Re, can cause up to 2 K/day difference in the radiative heating rates between algorithms.
Comparing the Detectability of Hepatocellular Carcinoma by C-Arm Dual-Phase Cone-Beam Computed Tomography During Hepatic Arteriography With Conventional Contrast-Enhanced Magnetic Resonance Imaging
Purpose: To evaluate the sensitivity of dual-phase cone-beam computed tomography during hepatic arteriography (CBCTHA) for the detection of hepatocellular carcinoma (HCC) by comparing it with the diagnostic imaging 'gold standard': contrast-enhanced magnetic resonance imaging (CE-MRI) of the liver. Materials and Methods: Eighty-eight HCC lesions (mean diameter 3.9 {+-} 3.3 cm) in 20 patients (13 men, mean age 61.4 years [range 50 to 80]), who sequentially underwent baseline diagnostic liver CE-MRI and then underwent early arterial- and delayed portal venous-phase CBCTHA during drug eluting-bead transarterial chemoembolization, were evaluated. Dual-phase CBCTHA findings of each tumor in terms of conspicuity were compared with standard CE-MR images and classified into three grades: optimal, suboptimal, and nondiagnostic. Results: Seventy-seven (mean diameter 4.2 {+-} 3.4 cm [range 0.9 to 15.9]) (93.9%) of 82 tumors were detected. Sensitivity of arterial-phase (71.9%) was lower than that of venous-phase CBCTHA (86.6%) for the detection of HCC lesions. Of the 82 tumors, 33 (40.2%) and 52 (63.4%), 26 (31.7%) and 19 (23.2%), and 23 (28%) and 11 (13.4%) nodules were classed as optimal, suboptimal, and nondiagnostic on arterial- and venous-phase CBCTHA images, respectively. Seventeen (73.9%) of the 23 tumors that were not visible on arterial phase were detected on venous phase. Six (54.5%) of the 11 tumors that were not visible on venous phase were detected on arterial phase. Conclusions: Dual-phase CBCTHA has sufficient image quality to detect the majority of HCC lesions compared with the imaging 'gold standard': CE-MRI of the liver. Moreover, dual-phase CBCTHA is more useful and reliable than single-phasic imaging to depict HCC nodules.
Erratum to: Subclavian Vein Versus Arm Vein for Totally Implantable Central Venous Port for Patients with Head and Neck Cancer: A Retrospective Comparative Analysis
No abstract prepared.
Drug-Eluting Nitinol Stent Treatment of the Superficial Femoral Artery and Above-the-Knee Popliteal Artery (The Zilver PTX Single-Arm Clinical Study): A Comparison Between Diabetic and Nondiabetic Patients
Purpose: To describe the 1-year results of drug-eluting nitinol stent placement in the femoropopliteal artery of diabetic and nondiabetic patients. Materials and Methods: All patients enrolled in this prospective, multicenter study underwent paclitaxel-eluting stent placement for de novo or restenotic lesions of the superficial femoral and/or popliteal artery. Baseline and follow-up walking impairment questionnaire (WIQ) scores, Rutherford classifications, and ankle-brachial index (ABI) measurements were obtained. Follow-up was completed at 1, 6, and 12 months. Results: There were 285 diabetic patients and 502 nondiabetic patients treated. There were no significant differences in mean lesion length or lesion calcification between patient groups. Procedural success in both treatment groups was >97 %. There were no significant differences between diabetic and nondiabetic groups in Kaplan-Meier estimates of patency, event-free survival (EFS), or freedom from target lesion revascularization (TLR) at 6 and 12 months. Both groups experienced a significant increase in ABI and WIQ values after treatment, and these improvements were sustained to 12-month follow-up; however, nondiabetic patients had significantly greater 6- and 12-month WIQ scores compared with diabetic patients. Based on covariate analysis, the only factors shown to be significant and to negatively influence patency were longer lesion length (p = 0.009), higher Rutherford classification (p = 0.02), and lack of hypertension (p = 0.02); diabetic status was not found to be a significant factor. Conclusion: Diabetic and nondiabetic patients had similar estimates of primary patency, EFS, and freedom from TLR; however, diabetic patients showed less improvement in WIQ scores compared with nondiabetic patients.
The Use of Laser Guidance Reduces Fluoroscopy Time for C-Arm Cone-Beam Computed Tomography-Guided Biopsies
PurposeWhen using laser guidance for cone-beam computed tomography (CBCT)-guided needle interventions, planned needle paths are visualized to the operator without the need to switch between entry- and progress-view during needle placement. The current study assesses the effect of laser guidance during CBCT-guided biopsies on fluoroscopy and procedure times.Materials and MethodsProspective data from 15 CBCT-guided biopsies of 8–65 mm thoracic and abdominal lesions assisted by a ceiling-mounted laser guidance technique were compared to retrospective data of 36 performed CBCT-guided biopsies of lesions >20 mm using the freehand technique. Fluoroscopy time, procedure time, and number of CBCT-scans were recorded. All data are presented as median (ranges).ResultsFor biopsies using the freehand technique, more fluoroscopy time was necessary to guide the needle onto the target, 165 s (83–333 s) compared to 87 s (44–190 s) for laser guidance (p < 0.001). Procedure times were shorter for freehand-guided biopsies, 24 min versus 30 min for laser guidance (p < 0.001).ConclusionThe use of laser guidance during CBCT-guided biopsies significantly reduces fluoroscopy time.
Laser Guidance in C-Arm Cone-Beam CT-Guided Radiofrequency Ablation of Osteoid Osteoma Reduces Fluoroscopy Time
PurposeTo assess whether laser guidance can reduce fluoroscopy and procedure time of cone-beam computed tomography (CBCT)-guided radiofrequency (RF) ablations of osteoid osteoma compared to freehand CBCT guidance.Materials and Methods32 RF ablations were retrospectively analyzed, 17 laser-guided and 15 procedures using the freehand technique. Subgroup selection of 18 ablations in the hip–pelvic region with a similar degree of difficulty was used for a direct comparison. Data are presented as median (ranges).ResultsComparison of all 32 ablations resulted in fluoroscopy times of 365 s (193–878 s) for freehand and 186 s (75–587 s) for laser-guided procedures (p = 0.004). Corresponding procedure times were 56 min (35–97 min) and 52 min (30–85 min) (p = 0.355). The subgroup showed comparable target sizes, needle path lengths, and number of scans between groups. Fluoroscopy times were lower for laser-guided procedures, 215 s (75–413 s), compared to 384 s (193–878 s) for freehand (p = 0.012). Procedure times were comparable between groups, 51 min (30–72 min) for laser guidance and 58 min (35–79 min) for freehand (p = 0.172).ConclusionAdding laser guidance to CBCT-guided osteoid osteoma RF ablations significantly reduced fluoroscopy time without increasing procedure time.Level of EvidenceLevel 4, case series.
Clinical Experience with Real-Time 3-D Guidance Based on C-Arm-Acquired Cone-Beam CT (CBCT) in Transjugular Intrahepatic Portosystemic Stent Shunt (TIPSS) Placement
PurposeThe aim of this study was to evaluate the feasibility of cone-beam computed tomography (CBCT)-based real-time 3-D guidance of TIPSS placement and its positioning compared to standard guiding methods.Materials and MethodsIn a prospective, randomized, consecutive study design from 2015 to 2017, we included 21 patients in the CBCT guided group and 15 patients in the ultrasound (US) guided group. The prospective groups were compared in terms of success rate of intervention, portal vein puncture/procedure time, number of puncture attempts and applied dose. We furthermore retrospectively analyzed the last 23 consecutive cases with fluoroscopic guided portal vein puncture in terms of success rate, procedure time and applied dose, as it has been the standard method before US guidance.ResultsThe median number of puncture attempts (CBCT: n = 2, US: n = 4, p = 0.249) and the mean puncture time (CBCT: 32 ± 45 min, US: 36 ± 45 min, p = 0.515) were not significantly different. There were furthermore no significant differences in the mean time needed for the total TIPSS procedure (CBCT: 115 ± 52 min, US: 112 ± 41 min, fluoroscopy: 110 ± 33 min, p = 0.996). The mean applied dose of the complete procedure also showed no statistically significant differences (CBCT: 563 ± 289 Gy·cm{sup 2}, US: 322 ± 186 Gy·cm{sup 2}, fluoroscopy: 469 ± 352 Gy·cm{sup 2}, p = 0.069). There were no image guidance related complications.ConclusionReal-time 3-D needle guidance based on CBCT is feasible for TIPSS placement. In terms of puncture attempts, duration and dose, CBCT guidance was not inferior to the control groups and may be a valuable support for interventionists in TIPSS procedures.
Application of a Metal Artifact Reduction Algorithm for C-Arm Cone-Beam CT: Impact on Image Quality and Diagnostic Confidence for Bronchial Artery Embolization
Objective: The objective of this study was to evaluate the potential benefit of a dedicated cone-beam-CT streak metal artifact removal technique (SMART) in terms of both image quality and diagnostic confidence in patients undergoing bronchial artery embolization. Methods: A total of 17 patients were included in this retrospective study. The SMART algorithm was applied to images containing streak artifacts generated by a radiopaque intra-arterial catheter tip. Quantitative evaluation of artifact severity was performed via measurement of the Hounsfield units along a closed loop surrounding the catheter tip and was conducted in the frequency domain following the application of the discrete Fourier transform to the measured data. A high proportion of power in the low frequencies of the resulting spectrum indicated a high level of streak artifacts. Qualitative evaluation of diagnostic confidence was performed using a 4-point Likert scale. Results: Both quantitative and qualitative evaluation demonstrated a significant reduction in artifact severity using the SMART algorithm. Quantitative evaluation demonstrated a mean artifact reduction of 22.5% using SMART compared to non-SMART images (p < 0.001). Qualitative evaluation demonstrated the greatest artifact reduction at the inner and outer aortic curvature, as well as immediately surrounding the tip of the catheter. In 6 of 17 cases, the use of the SMART algorithm yielded additional clinical information, increasing mean diagnostic confidence from 3.17 to 3.78 (p < 0.001). Conclusion: The SMART algorithm allows for efficient reduction of metal artifacts introduced by radiopaque catheter tips during cone-beam CT. Using this algorithm, diagnostic images of the aortic arch were significantly improved both quantitatively and qualitatively, yielding clinically relevant levels of enhanced diagnostic confidence. These results demonstrate that the SMART algorithm improves diagnostic and clinical characterization of the course of bronchial arteries on CBCT images, potentially improving the accuracy and clinical efficacy of bronchial artery embolization. Level of Evidence: 3.
A reliability-aware multi-armed bandit approach to learn and select users in demand response
Not Available
Adenovirus armed with VGLL4 selectively kills hepatocellular carcinoma with G2/M phase arrest and apoptosis promotion
Highlights: • VGLL4 causes G2/M phase arrest in hepatocellular carcinoma cells. • The transcription level of VGLL4 gene is promoted by oncolytic adenovirus. • Oncolytic adenovirus harboring VGLL4 selectively kills hepatocellular carcinoma. • Oncolytic adenovirus harboring VGLL4 exerts G2/M arrest and apoptosis promotion. The Vestigial-Like Family Member 4 (VGLL4) functions as a native inhibitor of cell proliferation and tumor growth through multiple signaling pathways. We first discovered that VGLL4 causes G2/M phase arrest in hepatocellular carcinoma (HCC) cells. Then, we designed a novel survivin-regulated oncolytic adenovirus Ad-sp-VGLL4 carrying the VGLL4 gene. Ad-sp-VGLL4 exerted high HCC-targeting-selectivity but is less harmful to normal cells. This adenovirus construction enhanced antitumor activity due to G2/M phase arrest and enhanced apoptosis. It's also indicated that Ad-sp-VGLL4 could suppress the growth of transplanted tumor of HCC in vivo experiment. Taken together, our results suggest that Ad-sp-VGLL4 possesses strong antitumor capacity and has great potential use for HCC therapy.
Global Electric Circuit research at Graciosa Island (ENA-ARM facility): First year of measurements and ENSO influences
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